The goal of this proposal is to capture the progression of events and responses to these events in the everyday life of middle-aged and older individuals. The Health and Retirement Study (HRS) has provided major insights into the lives of middle-aged and older individuals based on interviews every two years. The proposed study aims to advance further understanding through the use of intensive data collection and an innovative design that allows very detailed and comprehensive data collection proximal to events hypothesized to impact health and wellbeing, including but not limited to retirement. First, we plan to administer the core HRS instrument every two years in the Understanding America Study (UAS, a probability-based Internet panel), so that we have direct comparability with the HRS. Second, we will monitor important events in the lives of older UAS respondents with brief, monthly assessments via the Internet, which will include anticipated events (e.g. retirement, job change, change in marital status) and unanticipated events (e.g. deaths, illnesses, job change); these assessments will signal an immediate intensive “burst” of data collection in order to better link changes in life circumstances, health, behaviors, and well-being. Third, the intensive assessments will track multiple domains of variables on a daily basis over an entire week, including daily pain, fatigue, physical functioning, stress, wellbeing, exercise, diet, social interaction, sleep, and cognitive function. Fourth, the event- based burst measurements will be embedded in the context of regular, annual intensive measurement bursts, which serve as baselines for evaluating the impact of events. Fifth, we plan to conduct experiments within the intensive assessments of the feasibility and utility of wearable sensors, some of which may be adopted for permanent use in the study design. Overall, the goal is to provide a much richer picture of people's daily lives both before and after retirement and other life events that will enable the study of pathways to many outcomes, such as financial and subjective wellbeing, health, cognitive functioning, and social engagement. We expect these data to be a valuable resource for the research community as it moves to more internet interviewing and use of novel measurement devices.